What I mean is that in the definition of the "field", for example:
'website_title' => array(there is already a 'size' attribute.
'type' => 'text',
'label' => $txt['website_title'],
'subtext' => $txt['include_website_url'],
'size' => 50,
'permission' => 'profile_extra',
'link_with' => 'website',
This 'size' is used to define the input box size, the only reason I didn't yet apply the change is that this size will affect many fields at the same time (including passwords).
I would avoid adding yet another attribute just to set the limits of the field, so I'm wondering if it is better to continue use the size for the input box and set the limits to the double of that amount (i.e. website title has size 50, it will be cut at 100 chars) or use the size to define the string limit and set the size of the input box to the half of it (i.e. set size for website_title to 100 and then cut the $_POST to 100 and draw the input at 50 (=100/2))
...for compatibility the first is better I think.